使用R复制文件 [英] using R to copy files

问题描述

作为在Windows下执行的更大任务的一部分，我想在目录之间复制所选文件。是否可以在R中给出 cp patha / filea * .csv pathb （注意通配符，额外的香料）的命令？

As part of a larger task performed in R run under windows, I would like to copy selected files between directories. Is it possible to give within R a command like cp patha/filea*.csv pathb (notice the wildcard, for extra spice)?

推荐答案

我不认为有一个直接的方式（害怕的shelling-out），但像下面的东西通常适用于我。

I don't think there is a direct way (shy of shelling-out), but something like the following usually works for me.

flist <- list.files("patha", "^filea.+[.]csv$", full.names = TRUE)
file.copy(flist, "pathb")

注意：

• 我故意分两步，可以合并。


• 查看正则表达式：R使用true正则表达式，并且还在两个单独的参数中将文件模式与路径分开。


• 请注意 ^ 和 $ （beg / end of string）在regex中 - 这是一个常见的陷阱，因为这些是通配符类型模式，但是需要regex


• 在Windows环境中，用户通常会添加 ignore.case = TRUE 参数 list.files ，以模拟目录搜索对此操作系统不区分大小写的事实。


• R的 glob2rx（）函数提供了一种将通配符模式转换为正则表达式的便捷方法。例如 fpattern = glob2rx（'filea * .csv'）返回不同的但等价的正则表达式。

• I purposely decomposed in two steps, they can be combined.
• See the regular expression: R uses true regex, and also separates the file pattern from the path, in two separate arguments.
• note the ^ and $ (beg/end of string) in the regex -- this is a common gotcha, as these are implicit to wildcard-type patterns, but required with regexes (lest some file names which match the wildcard pattern but also start and/or end with additional text be selected as well).
• In the Windows world, people will typically add the ignore.case = TRUE argument to list.files, in order to emulate the fact that directory searches are case insensitive with this OS.
• R's glob2rx() function provides a convenient way to convert wildcard patterns to regular expressions. For example fpattern = glob2rx('filea*.csv') returns a different but equivalent regex.

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